CORDIC convenience , adapted from http://www.dcs.gla.ac.uk/~jhw/cordic/

cordic-32bit-test.c

#include <stdio.h>         // for printf
#include <math.h>          // for testing only, not used by cordic
#include "cordic-32bit.h"  // for actual cordic algo

//Print out sin(x) vs fp CORDIC sin(x)
int main(int argc, char **argv)
{
    float p;
    // sin_int, cos_in;
    float sin_float, cos_float, mathh_sin_float;
    int i;    
    for(i=0;i<100;i++)
    {
        p = -4*M_PI + (i/100.0)*8*M_PI;        

        // how to use 'raw' cordic
        // cordic((p*MUL), &sin_int, &cos_int, 32);

        // how to use 'convenient' cordic
        cordic_float_convenience(p, &sin_float, &cos_float, 32);

        //these values should be nearly equal
        mathh_sin_float = sin(p);
        printf("SIN(% 2.6f * PI), cordic = % 2.6f, math.h = % 2.6f, error = % e\n",
            p/M_PI, sin_float, mathh_sin_float, sin_float - mathh_sin_float);
    }       
}

cordic-32bit.h

// cordic-32bit.h

#ifndef CORDIC_32_BIT_H
#define CORDIC_32_BIT_H

#include <math.h>

// #define M_PI 3.1415926535897932384626
#define K1 0.6072529350088812561694

//Cordic in 32 bit signed fixed point math
//Function is valid for arguments in range -pi/2 -- pi/2
//for values pi/2--pi: value = half_pi-(theta-half_pi) and similarly for values -pi---pi/2
//
// 1.0 = 1073741824
// 1/k = 0.6072529350088812561694
// pi = 3.1415926535897932384626
//Constants
#define cordic_1K 0x26DD3B6A
#define half_pi 0x6487ED51
#define CORDIC_MUL 1073741824.000000
#define CORDIC_NTAB 32
int cordic_ctab [] = {0x3243F6A8, 0x1DAC6705, 0x0FADBAFC, 0x07F56EA6, 0x03FEAB76, 0x01FFD55B, 
0x00FFFAAA, 0x007FFF55, 0x003FFFEA, 0x001FFFFD, 0x000FFFFF, 0x0007FFFF, 0x0003FFFF, 
0x0001FFFF, 0x0000FFFF, 0x00007FFF, 0x00003FFF, 0x00001FFF, 0x00000FFF, 0x000007FF, 
0x000003FF, 0x000001FF, 0x000000FF, 0x0000007F, 0x0000003F, 0x0000001F, 0x0000000F, 
0x00000008, 0x00000004, 0x00000002, 0x00000001, 0x00000000, };

void cordic(int theta, int *s, int *c, int n)
{
  int k, d, tx, ty, tz;
  int x=cordic_1K,y=0,z=theta;
  n = (n>CORDIC_NTAB) ? CORDIC_NTAB : n;
  for (k=0; k<n; ++k)
  {
    d = z>>31;
    //get sign. for other architectures, you might want to use the more portable version
    //d = z>=0 ? 0 : -1;
    tx = x - (((y>>k) ^ d) - d);
    ty = y + (((x>>k) ^ d) - d);
    tz = z - ((cordic_ctab[k] ^ d) - d);
    x = tx; y = ty; z = tz;
  }  
 *c = x; *s = y;
}

void cordic_float_convenience(float theta, float *sin_float, float *cos_float, int n) {
    int sin_int, cos_int;
    float sign_mult;
    float tm = fmodf(theta + M_PI/2, 2*M_PI);

    if(tm >= 0) {                  // POS THETA BRANCH
        if(tm <= M_PI) {               // POS OUT CASE
            sign_mult = 1.0f;
            theta = tm - M_PI/2;
        }
        else {                         // NEG OUT CASE
            sign_mult = -1.0f;
            theta = tm - 3*M_PI/2;
        }
    }
    else {                         // NEG THETA BRANCH
        if(tm >= -M_PI) {              // NEG OUT CASE
            sign_mult = -1.0;
            theta = tm + M_PI/2;
        }
        else {                         // POS OUT CASE
            sign_mult = 1.0;
            theta = tm + 3*M_PI/2;
        }
    }
        
    cordic(theta*CORDIC_MUL, &sin_int, &cos_int, n);
    *sin_float = sign_mult * sin_int/CORDIC_MUL;
    *cos_float = sign_mult * cos_int/CORDIC_MUL;
}

#endif